REFLEX ACTION ::
It is an instantaneous involuntary effector response produced due to an affector sensory stimulus which passes through a nerve in spinal cord it is a part of the defence mechanism of the body and its action is more rapid than the voluntary actions e.g. closing of the eye when a foreign body e.g .dust or mosquito comes near withdrawal of hand when it accidentally touches a hot surface Reflex action arises out of the nerve impulses passing through a reflex are with its centre in the spinal cord
Reflex Are::
It incorporates the following
1.The sensory organ which receives the impulses e.g. skin
2. The sensory nerve fibre conducts impulses to the cells in the posterior root ganglion and then to the gray matter of the posterior horn of the spinal cord
3. The gray matter of spinal cord through which connector nerves pass on the impulses to the anterior horn of the spinal cord
4. A motor nerve cell in the anterior horn of the spinal cord transmitting impulses along the respective motor nerve fibres
5. A motor organ e.g muscle it is stimulated by the motor nerve impulses coming from the anterior nerve horn cells
The reflex arcs are of three types ::
a.Monosynaptic : i.e. involving only one synapse e.g. stretch reflex of the muscles
b.Disynaptic i.e. involving two synapses i.e. one between afferent and an
intermediate neurone and other between efferment and an intermediate neurone
e.g. extension reflex
c.polysypnaptic : i.e. involving many intermediate neurons and effectores e.g withdrawal reflex
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